The effects of some cellular and environmental variables on the histogenetic behavior in vitro of two related human cervical squamous carcinoma cell lines were investigated. The differences between the cell lines in stratification and colony morphology appeared due primarily to differences in the relative strength of intercellular cohesion and adhesiveness to substrata rather than to differences in cell-surface charges, cell-coat mucoproteins, contact inhibition, or nutritional factors. These differences in adhesiveness could be correlated with ultrastructural cell-surface characteristics and with the differential roles of extracellular cations and proteins. Cytofilaments seemed important in the maintenance of culture morphology and in histogenetic movements related to cell crowding. Cell flattening and junctional-complex formation were identified as direct responses to a liquid environment, since the formation of these cell modifications could be controlled by changes in environmental solidity.